Preimplantation Genetic Diagnosis (PGD)
With 99.9% accuracy in predicting an embryo’s gender, PGD gives couples the best odds in determining their baby’s sex. But unlike MicroSort®, which is used prior to conception, PGD is performed after conception using IVF. This poses a moral or ethical dilemma for some couples because they’re creating embryos, some of which may not be used. They consequently have to decide what to do with the excess embryos. Other than this concern, PGD offers couples the best bet in selecting their future baby’s gender.
A relatively new reproductive technology, PGD allows couples to choose their baby’s sex by identifying male and female embryos conceived in a laboratory, prior to transfer to the woman’s uterus. PGD requires IVF, fertilization in a lab dish, along with a minor surgical procedure to remove eggs from her ovaries. After fertilization, specialists examine the 2-day-old embryo for its sex chromosomes (XX or XY), and inserts one or several embryos of the selected sex into the woman’s uterus.
PGD was first developed in the 1980s. Interestingly, the initial application of PGD in humans was to determine the gender of embryos to prevent X-linked genetic diseases This technique was first described in 1987 by scientists at the University of Edinburgh and the first live births, healthy twin girls, were reported in 1990. PGD has subsequently been used not only to detect gender but also to detect abnormalities of chromosome number, such as Down syndrome, and serious single-gene disorders such as cystic fibrosis and sickle-cell anemia.
With all methods of PGD, an important fact is worth noting: A surprisingly high percentage (50% to 70%) of embryos will be found to be abnormal, even in healthy, fertile couples. A typical PGD case might look something like this: 14 eggs are retrieved; 11 are suitable for fertilization; 8 fertilize; 6 are biopsied (one cell is examined); 3 are normal; and 1 or 2 of the normal embryos are of the desired gender. As you can see, this is a very inefficient process. Many couples who undergo IVF-PGD are often surprised by the high number of abnormal embryos they have in a cycle.
This news can be a shock when couples get the results of their embryo biopsies. But this is all part of nature — and it can help explain the many miscarriages that women experience as a whole. Not all of our eggs or embryos are healthy or free of chromosomal abnormalities, and most of them do not have the potential of turning into perfect little babies. But many embryos do. PGD can help Doctors sort out the “good eggs from the bad”, to borrow an expression. And it gives couples the opportunity to produce a healthy child of the gender they’re hoping for.
 S. J. D. West et al., “Sexing the Human Pre-Embryo by DNA – DNA in-situ hybridization,” Lancet 1 (1987): 1345–47.
 A. H. Handyside, E. H. Konotogianni, K. Hardy, and R.M. L. Winston, “Pregnancies from Biopsied Human Preimplantation Embryos Sexed by Y-Specific DNA Amplification,” Nature 334 (1990): 768–70.